Human prostatic acid phosphatase (PAP) has been used for diagnosis of prostate cancer, the most commonly found cancer in United States males. Human genomic clones containing PAP gene have been isolated and the exon-intron organization of PAP gene has been illustrated. The PAP gene was mapped to human chromosome 3q21-23. The expression of human PAP gene, as well as PSA (prostatic specific antigen) gene, in the benign and cancerous prostate tissues, has been investigated by Northern blot analysis.